1. Field of the Invention
The present invention relates generally to a combined receiver and speaker, in which the receiver and the speaker are combined into one structure, more particularly to a combined receiver and speaker, in which a speaker mounted on various kinds of mobile communication terminals such as mobile telephones including cellular phones, Personal Communication Service (PCS) phones, Personal Digital Assistants (PDA), International Mobile telecommunications (IMT)-2000 terminals and others and used for generating incoming sounds is combined with a receiver used for regenerating voice signals.
2. Description of the Prior Art
Generally, a speaker and a receiver included in a mobile communication terminal are equal to each other in terms of mechanical and electromagnetic structure. The speaker and the receiver are both designed to transduce electrical energy into mechanical energy by a voice coil in an air gap according to Fleming""s left hand rule stating that magnetic force is exerted on a conductor when the conductor through which current flows is in a magnetic field.
In other words, when a current signal including a variety of frequencies is applied to the voice coil, the voice coil generates mechanical energy according to current intensity and frequency level, and then a diaphragm attached to the voice coil is vibrated, such that a sound pressure of audible intensity is generated.
The receiver denotes a device usually generating a relatively low sound pressure among sound pressures and typically used while being in contact with the ears in use. Contrary to the receiver, the speaker denotes a device generating a relatively high sound pressure and typically used while being placed away from the ears in use.
Magnetic circuits of the speaker and the receiver are each designed such that a magnetic flux crosses the voice coil existing in the air gap at a right angle by using a magnet and an upper plate in a yoke made of iron, and the voice coil is attached to the diaphragm. Therefore, the voice coil generates exciting force by an input signal, thus allowing the diaphragm fixedly attached to a frame to vibrate so as to generate a sound pressure. The diaphragm has one of various wave shapes so as to obtain excellent response characteristics and remove a buckling phenomenon when it vibrates up and down, and the shape of this diaphragm functions as a design variable greatly affecting frequency characteristics.
The speaker and receiver have not been remarkably modified in structure for a long time. However, recently, the miniaturization, lightening and high efficiency of speakers and receivers are constantly implemented according to the commercialization of high energy permanence magnets, the development of microstructure shaping technology, and the trend toward miniaturization and lightening in data communication fields.
Especially, it is not too much to say that the miniaturization of a mobile communication terminal depends on whether or not the parts such as a receiver, speaker, buzzer or oscillator having mechanical dynamic characteristics can be miniaturized. Therefore, research and development for combining such mechanical parts have been actively performed.
Mostly, conventional mobile communication terminals have each long used a buzzer for generating call sounds. However, because a user demands the generation of various call sounds according to the user""s convenience and preference, the conventional buzzer has been replaced with a speaker having excellent frequency characteristics. Further, in the receiver, the improvement of frequency characteristics together with the miniaturization and lightening has become an important issue.
A conventional speaker and a receiver are mounted at different positions as separate parts when they are mounted on a mobile communication terminal.
A sectional view of FIG. 1 shows that in a conventional combined receiver and speaker, that outputs the sound signals and call sounds of the mobile communication terminal, in which a voice coil 5 with an impedance of 80xcexa9 and an impedance coil (HAC coil) 6 with an impedance of 32xcexa9 are mounted on a diaphragm 4 as separate parts.
In order to drive the diaphragm 4, voice current is outputted through lines respectively connected to the voice coil 5 and the impedance coil 6 in receiver and speaker modes, such that the diaphragm 4 can be driven in corresponding mode. In other words, exciting force generated by attraction force and repulsive force between a magnetic field due to the voice current flowing through the voice coil 5 or the impedance coil 6 and a magnetic field of the magnet 2 mounted on a frame 1 allows the diaphragm 4 fixedly mounted on the frame 1 to vibrate so as to generate a sound pressure.
Further, FIG. 2 is another sectional view showing a combined receiver and speaker, which is designed to implement receiver and speaker functions in different directions. Referring to FIG. 2, a diaphragm 14 for a receiver is arranged over a magnet 12 and an upper plate 13 mounted on a double yoke 11 in a frame 10, and a first voice coil 15 is mounted at a portion of the diaphragm 14. In addition, a diaphragm 16 for a speaker is arranged at the left side of the double yoke 11, and a second voice coil 17 is mounted on the diaphragm 16 to be inserted into the double yoke 11. In such a structure, the respective diaphragms 14 and 16 are arranged in different directions, such that they are driven by voice currents applied to the voice coils 15 and 17, respectively.
Therefore, the first conventional combined receiver and speaker, in which the voice coil and the impedance coil Mare arranged on one diaphragm, is problematic in that it is inconvenient to simultaneously mount the voice coil of 80xcexa9 and the impedance coil of 32xcexa9, and is decreased in its productivity and operation efficiency due to the difficult wiring process of the voice and impedance coils.
On the other hand, the second conventional combined receiver and speaker, in which the receiver and speaker functions are implemented in different directions, is problematic in that, because a double yoke must be additionally mounted on the frame and is constructed in opposite directions to arrange the voice coils of 80xcexa9 and 32xcexa9 at separate diaphragms so as to control impedance, it is difficult to miniaturize and integrate the receiver and speaker due to the limited space, and increases production costs because of more parts needed. Especially, in a speaker for generating call sounds, a diaphragm having a diameter comparatively larger than that of a receiver is required to output a sound pressure with a proper level, such that the combined receiver and speaker causes problems in its miniaturization.
As described above, in the conventional combined receiver and speaker, a voice coil for driving the diaphragm is mounted as a separate part to control impedance, such that an impedance control using the voice coil is difficult, causes a high failure rate, and increases costs.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a combined receiver and speaker, in which voice current is applied only to a voice coil in a speaker mode, while applied to both the voice coil and a chip resistor in a receiver mode, thus more effectively controlling impedance and easily achieving miniaturization and integration of the receiver and the speaker.
Another object of the present invention is to provide a combined receiver and speaker, which is constructed to arrange a single voice coil and a chip resistor in series so that the single voice coil is mounted at a portion of a diaphragm and the chip resistor is mounted at a portion of a frame, such that single directional and bi-directional speaker and receiver modes can be simultaneously operated, and only a bi-directional speaker mode can be operated, thus reducing the manufacturing costs and simplifying the operation process of the receiver combined with the speaker.
In order to accomplish the above object, the present invention provides a combined receiver and speaker comprising a diaphragm for generating sounds of a predetermined frequency through vibrations caused by a sound pressure in speaker and receiver modes; a voice coil for vibrating the diaphragm using a magnetic field formed around a magnet attached to the diaphragm and generated by applied voice current; and a chip resistor for decreasing the intensity of the applied voice current; wherein the voice current is selectively applied to the voice coil such that the voice current is applied to the voice coil from speaker terminals in speaker mode, while the voice current is applied to the voice coil via the chip resistor from receiver terminals in receiver mode.